The invention relates to a method for the cleaning of the matrix of a magnetic separator, whereby the matrix is cleaned with a liquid medium.
Furthermore, the invention relates to an apparatus for carrying out the method, and finally, a method for the operation of the apparatus.
Magnetic separators operating according to the hold-back principle are brought into use ordinarily for the handling of relatively large quantities of feed, for example in the range of 20 to 200 tons per hour. Additionally the separators are adapted in a special manner for the sorting of weakly magnetic minerals. The modus operandi os such hold-back wet magnetic separators in such that in a prescribed operating volume, the so-called separating chamber, a magnetic field as high as possible is produced, for example by means of the application of poles or in the inner chamber of a coil. Within this operating volume are located induction poles in the form of suitable magnetizable ferromagnetic bodies, which, on account of their high permeability, distort the magnetic field in such manner that strong inhomogeneities occur. Thus, the necessary gradients are produced at a plurality of preferred places in the volume of the separating chamber. The arrangement of the ferromagnetic body in a corresponding separating chamber is called the "matrix".
Upon the conveying through the matrix of a sludge laden with susceptible particles, the magnetic material contained in the sludge is held back on the ferromagnetic bodies on account of the high spatial magnetic forces. This held-back material is then ordinarily rinsed out of the matrix with a strong stream or jet of water.
This takes place with discontinuously or intermittently operating separators in such manner that the magnetic field is periodically disconnected and the magnetic material is rinsed out of the matrix in this disconnected condition. More and more, however, continuously operating separators are provided, as for example, the Jones Separator or the Carousel Separator.
In the case of such continuously operating separators, the magnetic material is moved out and washed out of the magnetic field with the matrix, after which the cleaned matrix is ready for the next passage through the magnetic field. According to the type of each magnetic material, it may also be necessary to clean the magnetic material from adherent non-magnetic material portions through a washing operation in the area of the magnetic field.
In addition, the necessity often arises of discharging intermediate products. This take place whereby within the magnetic field, a portion of the magnetic material is washed out with the adherent mine wastes with reduced rinsing energy.
As induction poles, there are employed in practice:
plates with projecting edges PA1 profiled rods PA1 loose balls or other loose spherical bodies PA1 expanded metal--packets or briquettes PA1 iron mesh--packings
The last named filler bodies, namely, balls, expanded metal, and iron mesh, are adapted on account of their fine structure to the concentration of particularly weak magnetic substances and/or particles with especially fine granular structure. This is favorable because, in the case of the plurality of induction poles at small spacing, even the smallest particles even if occurring in small number, have the possibility of reaching and being retained in an area of higher magnetic force.
On the other hand, however, the washing out of these particles through the ordinary cleaning of the matrix with a strong jet of water is difficult, if not actually impossible, because the dense packing of balls, expanded metal and the like breaks the stream of the cleaning medium and permits the same to pass only with low speed and low energy through the spaces between the plurality of induction poles. In this manner, the cleaning of the matrix remains incomplete, because the jet energy of the non-compressible cleaning liquid decreases with the distance from the nozzle, and thereby enters into effect only in the edge zones of the induction poles, while in deeper areas it is broken through the filter-like packing of the induction poles and therefore becomes ineffective.
Also the attempt to compensate for this disadvantage through the utilization of large quantities of liquid, brought only a small result and which also has the disadvantage that:
(1) for the cleaning, a large path--time portion becomes necessary with corresponding diminution of the feed through yield of the separator, and
(2) the large quantities of liquid make necessary more expensive clarification and separating apparatus, in order to separate the recovered solids from the cleaning liquid.